An electrochemical system either derives electrical energy from chemical reactions, or facilitates chemical reactions through the introduction of electrical energy. An electrochemical system generally includes a cathode, an anode, and an electrolyte, and is typically complex with multiple heterogeneous subsystems, multiple scales from nanometers to meters. On-line characterization of batteries or fuel cells in vehicles is difficult, due to very rough noisy environments.
In many battery-powered systems such as electric vehicles, laptops, and smartphones, accurate estimation of the battery state of power (SOP) is necessary to maximize system power throughput as well as to protect the battery from overcharging or discharging. It is challenging to predict the SOP, because the battery behavior is nonlinear when it is operated at its peak power. Traditional methods, such as hybrid pulse power characterization, have been used in the lab for SOP prediction but are generally not applicable for on-line applications due to the requirement for specific driving profiles.
Recently, a finite impulse response (FIR) filtering approach has been demonstrated to have great potential to estimate state of charge (SOC), as described in U.S. patent application Ser. No. 13/751,089, filed Jan. 27, 2013, entitled “METHODS AND APPARATUS FOR DYNAMIC ESTIMATION OF BATTERY OPEN-CIRCUIT VOLTAGE,” as well as U.S. patent application Ser. No. 13/646,663, filed Oct. 6, 2012, entitled “METHODS AND APPARATUS FOR DYNAMIC CHARACTERIZATION OF ELECTROCHEMICAL SYSTEMS” both of which are incorporated by reference herein as though fully set forth.
There remains a need for FIR-based methods that can predict battery SOP as well as SOC accurately in real time. In many applications of battery-powered systems such as electric vehicles, laptops, and smartphones, it is desirable to project battery power capabilities continuously, based on the present (evolving) battery conditions. These battery conditions include external environments such as temperatures and pressures, and internal conditions such as its age, its present state of charge and kinetics, etc.
A goal of SOP estimation is to calculate battery charge and discharge power capabilities, based on which a battery power management system can maximize the battery power efficiency without overcharge/discharge. Many recent commercial battery-powered systems do not include SOP estimators. In these products, battery charge/discharge currents and voltages are bounded by specific values which were predetermined by manufacturers. These current and voltage boundaries are predetermined to protect the battery from overcharge/discharge battery.
However, there are obvious drawbacks with these static limits. First of all, these limits don't reflect battery aging. Those boundaries for safe operation may need to be updated since they are may not be safe as a battery becomes old. Secondly, these limits tend to be conservative during the beginning life of battery because they were determined to accommodate many non-predictable factors. Yet for healthy batteries, it is safe to operate beyond these predetermined limits in most cases. Therefore a continuing need exists to regulate battery power outputs through dynamic, real-time adjustment of operational boundaries.